In a climate control system for heating or cooling a large building, a single circulation pump can be arranged to circulate a heat carrying fluid, such as water, steam or oil, to a large number of loads such as radiators. The circulation pump may be connected to a boiler or to a heat exchanger of a primary heating system. The flow in the system is typically controlled by balancing valves, each one controlling the flow to a branch of radiators. In addition to these valves, there may be master control valves, controlling the flow to a group of balancing valves. For example, in a multi building system there may be one master control valve for each building, and a set of balancing valves on the ground floor of each building, each balancing valve connected to a set of apartments.
The balancing valves and master control valves distribute the flow from the circulation pump to each radiator, where a manual valve or thermostat reduces this maximum flow to a required flow.
Under these circumstances, it is a well-known challenge to adjust all control points of the system to provide the desired fluid flow and heating/cooling power in all parts of the system. Typically, even is such an adjustment is successfully completed for a building, it will not be maintained for very long, as there is a risk that someone will be tempted to make a manual adjustment at some point for some reason.
Also, and even more importantly, a sub-optimal flow control may lead to a decreased system efficiency, potentially requiring an increase in system temperature (i.e. temperature of the medium distributed by the circulation pump).
In order to mitigate this problem, and provide a more optimal flow control, some providers of heating systems provide a solution fixed flow regulators are installed throughout the system. These fixed flow regulators are used instead of the balancing valves and master control valves, and may be installed in connection with the thermostat of each radiator. Each such fixed flow regulator has a defined valve coefficient (CV), representing a relationship between flow and pressure. More specifically, a CV of 1.0 indicates that the flow regulator will provide a flow of 1 cubic meter per hour at a differential pressure of 1 bar. Document EP 125 239 discloses an example of such a system.
The present applicant, QSEC Sverige AB in Askim, Sweden offer heating system control based on such fixed flow regulators. In order to determine the appropriate flow in each control point, and thus the appropriate fixed flow regulator, QSEC have developed a software which creates a mathematical model of the entire heating system, including e.g. all pipes and radiators. The model is based on available schematics of the system, together with detailed characteristics of each component indicated in the schematics.
Based on the computer model, the system is configured to determine a maximum flow in each radiator given a set circulation pump pressure. The system further determines pressure drops throughout the system required to achieve these flows, and thus appropriate valve coefficients (Cv). By installing fixed flow regulators having these Cv-values, a more optimal (and more permanent) adjustment of the system can be achieved, and as a consequence the required system temperature can be minimized thereby saving cost.
However, despite all efforts, the system may still deviate from the intended performance. One reason is that in some cases the mathematical model is unable to perfectly model the actual heating system behavior. To begin with, the properties of the actual system may deviate from those indicated in the schematics, e.g. because one or several components have been replaced. Further, the system may be subject to external influence with time, such as repeated painting of a radiator (leading to reduced heat transmission) or an indentation of a pipe (leading to a reduced flow—and increased pressure drop—in this pipe). Other processes that may influence the system performance is rust (potentially leading to a smaller inner diameter of a pipe) and compression of isolation in a wall (leading to reduced isolation of a pipe in that wall).
As consequence, the resulting temperature may be unsatisfactory in one or several rooms or apartments. When this happens, a manual adjustment is sometimes performed (typically during winter), e.g. increasing the Cv-value in a room which is too cold by simply replacing the fixed flow regulator. However, such adjustments will typically lead to an additional error or series of errors in other parts of the system, and it will be difficult (and very time consuming) to achieve an adjustment according to what was originally intended.